Extended measurement word determination at a channel subsystem of an I/O processing system

ABSTRACT

An article of manufacture, an apparatus, and a method for determining an extended measurement word at a channel subsystem of an I/O processing system using data from a control unit are provided. The article of manufacture includes at least one computer usable medium having computer readable program code logic. The computer readable program code logic performs a method including sending a command message to the control unit, and receiving a transport response information unit message at the channel subsystem in response to sending the command message to the control unit. The computer readable program code logic additionally extracts a plurality of time values from the transport response information unit message as calculated by the control unit, calculates an extended measurement word as a function of the time values, and writes the extended measurement word to computer readable memory in the I/O processing system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates generally to input/output processing, andin particular, to providing feedback data associated with input/outputprocessing to a channel subsystem.

2. Description of Background

Input/output (I/O) operations are used to transfer data between memoryand I/O devices of an I/O processing system. Specifically, data iswritten from memory to one or more I/O devices, and data is read fromone or more I/O devices to memory by executing I/O operations.

To facilitate processing of I/O operations, an I/O subsystem of the I/Oprocessing system is employed. The I/O subsystem is coupled to mainmemory and the I/O devices of the I/O processing system and directs theflow of information between memory and the I/O devices. One example ofan I/O subsystem is a channel subsystem. The channel subsystem useschannel paths as communications media. Each channel path includes achannel coupled to a control unit, the control unit being furthercoupled to one or more I/O devices.

The channel subsystem may employ channel command words (CCWs) totransfer data between the I/O devices and memory. A CCW specifies thecommand to be executed. For commands initiating certain I/O operations,the CCW designates the memory area associated with the operation, theaction to be taken whenever a transfer to or from the area is completed,and other options.

During I/O processing, a list of CCWs is fetched from memory by achannel. The channel parses each command from the list of CCWs andforwards a number of the commands, each command in its own entity, to acontrol unit coupled to the channel. The control unit then processes thecommands. The channel tracks the state of each command and controls whenthe next set of commands are to be sent to the control unit forprocessing. The channel ensures that each command is sent to the controlunit in its own entity. Further, the channel infers certain informationassociated with processing the response from the control unit for eachcommand.

Performing I/O processing on a per CCW basis may involve a large amountof processing overhead for the channel subsystem, as the channels parseCCWs, track state information, and react to responses from the controlunits. Therefore, it may be beneficial to shift much of the processingburden associated with interpreting and managing CCW and stateinformation from the channel subsystem to the control units. Simplifyingthe role of channels in communicating between the control units and anoperating system in the I/O processing system may increase communicationthroughput as less handshaking is performed. However, altering commandsequences, as well as roles of the channel subsystem and the controlunits, can cause difficulties in maintaining legacy informationassociated with the I/O processing. Timer values used to verify variousportions of a successful command sequence may be unavailable at thechannel subsystem without enhanced messaging from the control units toprovide extended measurement data. Such enhanced messaging wouldnecessitate additional functionality in both the control units and thechannel subsystem to provide and use the extended measurement data.Accordingly, there is a need in the art for determining an extendedmeasurement word at a channel subsystem of an I/O processing systembased on extended measurement word data provided by a control unit ofthe I/O processing system.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention include an article of manufacture thatincludes at least one computer usable medium having computer readableprogram code logic to determine an extended measurement word at achannel subsystem of an I/O processing system using data from a controlunit. The computer readable program code logic performs a methodincluding sending a command message to the control unit, and receiving atransport response information unit message at the channel subsystem inresponse to sending the command message to the control unit. Thecomputer readable program code logic additionally extracts a pluralityof time values from the transport response information unit message ascalculated by the control unit, calculates an extended measurement wordas a function of the time values, and writes the extended measurementword to computer readable memory in the I/O processing system.

Additional embodiments include an apparatus for determining an extendedmeasurement word in an I/O processing system. The apparatus includes achannel subsystem in communication with a control unit, where thecontrol unit is capable of commanding and determining status of an I/Odevice. The channel subsystem sends a command message to the controlunit, and receives a transport response information unit message at thechannel subsystem in response to sending the command message to thecontrol unit. The channel subsystem further extracts a plurality of timevalues from the transport response information unit message ascalculated by the control unit, calculates an extended measurement wordas a function of the time values, and writes the extended measurementword to computer readable memory in the I/O processing system.

Further embodiments include a method for determining an extendedmeasurement word at a channel subsystem of an I/O processing systemusing data from a control unit. The method includes sending a commandmessage to the control unit, and receiving a transport responseinformation unit message at the channel subsystem in response to sendingthe command message to the control unit. The method also includesextracting a plurality of time values from the transport responseinformation unit message as calculated by the control unit, calculatingan extended measurement word as a function of the time values, andwriting the extended measurement word to computer readable memory in theI/O processing system.

An additional embodiment includes an article of manufacture including atleast one computer usable medium having computer readable program codelogic to determine an extended measurement word at a channel subsystemof an I/O processing system using data from a control unit. The computerreadable program code logic performs a method including sending atransport command information unit message including a transport commandcontrol block (TCCB) as part of a transport control word (TCW) channelprogram to the control unit for execution. The computer readable programcode logic receives a transport response information unit message at thechannel subsystem in response to sending the transport commandinformation unit message to the control unit, where the transportresponse information unit message includes a status section and anextended status section. The extended status section further includes atransport status header (TSH) defining characteristics of a transportstatus area (TSA) of the extended status section. The computer readableprogram code logic also extracts a plurality of time values from theextended status section of the transport response information unitmessage as calculated by the control unit using one or more control unittimers, where the plurality of time values include at least one of atotal device time parameter, a defer time parameter, a queue timeparameter, a device busy time parameter, a device active only timeparameter, and appended device sense data. The computer readable programcode logic additionally calculates an extended measurement word as afunction of the time values, where the extended measurement wordincludes at least one of a device connect time, a function pending time,a device disconnect time, a control unit queuing time, a device activeonly time, a device busy time, and an initial command response time. Thecomputer readable program code logic writes the extended measurementword to computer readable memory in the I/O processing system.

A further embodiment includes an apparatus for determining an extendedmeasurement word in an I/O processing system. The apparatus includes achannel subsystem in communication with a control unit. The control unitis capable of commanding and determining status of an I/O device. Thechannel subsystem sends a transport command information unit messageincluding a transport command control block (TCCB) as part of atransport control word (TCW) channel program to the control unit forexecution. The channel subsystem also receives a transport responseinformation unit message at the channel subsystem in response to sendingthe transport command information unit message to the control unit,where the transport response information unit message includes a statussection and an extended status section. The extended status sectionfurther including a transport status header (TSH) definingcharacteristics of a transport status area (TSA) of the extended statussection. The channel subsystem additionally extracts a plurality of timevalues from the extended status section of the transport responseinformation unit message as calculated by the control unit using one ormore control unit timers, where the plurality of time values include atleast one of a total device time parameter, a defer time parameter, aqueue time parameter, a device busy time parameter, a device active onlytime parameter, and appended device sense data. The channel subsystemfurther calculates an extended measurement word as a function of thetime values, where the extended measurement word includes at least oneof a device connect time, a function pending time, a device disconnecttime, a control unit queuing time, a device active only time, a devicebusy time, and an initial command response time. The channel subsystemwrites the extended measurement word to computer readable memory in theI/O processing system.

Other articles of manufacture, apparatuses, and/or methods according toembodiments will be or become apparent to one with skill in the art uponreview of the following drawings and detailed description. It isintended that all such additional articles of manufacture, apparatuses,and/or methods be included within this description, be within the scopeof the present invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other objects, features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 depicts one embodiment of an I/O processing system incorporatingand using one or more aspects of the present invention;

FIG. 2 a depicts one example of a prior art channel command word;

FIG. 2 b depicts one example of a prior art channel command word channelprogram;

FIG. 3 depicts one embodiment of a prior art link protocol used incommunicating between a channel and control unit to execute the channelcommand word channel program of FIG. 2 b;

FIG. 4 depicts one embodiment of a transport control word channelprogram, in accordance with an aspect of the present invention;

FIG. 5 depicts one embodiment of a link protocol used to communicatebetween a channel and control unit to execute the transport control wordchannel program of FIG. 4, in accordance with an aspect of the presentinvention;

FIG. 6 depicts one embodiment of a prior art link protocol used tocommunicate between a channel and control unit in order to execute fourread commands of a channel command word channel program;

FIG. 7 depicts one embodiment of a link protocol used to communicatebetween a channel and control unit to process the four read commands ofa transport control word channel program, in accordance with an aspectof the present invention;

FIG. 8 depicts one embodiment of a control unit and a channel, inaccordance with an aspect of the present invention;

FIG. 9 depicts one embodiment of a response message communicated from acontrol unit to a channel, in accordance with an aspect of the presentinvention;

FIG. 10 depicts one embodiment of a timing diagram for channel andcontrol unit measurements of an I/O operation;

FIG. 11 depicts one embodiment of a process for determining an extendedmeasurement word at a channel subsystem of an I/O processing systemusing data from a control unit; and

FIG. 12 depicts one embodiment of an article of manufactureincorporating one or more aspects of the present invention.

The detailed description explains the preferred embodiments of theinvention, together with advantages and features, by way of example withreference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with an aspect of the present invention, input/output(I/O) processing is facilitated. For instance, I/O processing isfacilitated by readily enabling access to information, such as statusand measurement data, associated with I/O processing. Further, I/Oprocessing is facilitated, in one example, by reducing communicationsbetween components of an I/O processing system used to perform the I/Oprocessing. For instance, the number of exchanges and sequences betweenan I/O communications adapter, such as a channel, and a control unit isreduced. This is accomplished by sending a plurality of commands fromthe I/O communications adapter to the control unit as a single entityfor execution by the control unit, and by the control unit sending thedata resulting from the commands, if any, as a single entity.

The plurality of commands are included in a block, referred to herein asa transport command control block (TCCB), an address of which isspecified in a transport control word (TCW). The TCW is sent from anoperating system or other application to the I/O communications adapter,which in turn forwards the TCCB in a command message to the control unitfor processing. The control unit processes each of the commands absent atracking of status relative to those individual commands by the I/Ocommunications adapter. The plurality of commands is also referred to asa channel program, which is parsed and executed on the control unitrather than the I/O communications adapter.

In an exemplary embodiment, the control unit generates a responsemessage including status and extended status information in response toexecuting the channel program. The control unit may also generate aresponse message without executing the channel program under a limitednumber of communication scenarios, e.g., to inform the I/Ocommunications adapter that the channel program will not be executed.The control unit may include a number of elements to supportcommunication between the I/O communications adapter and I/O devices, aswell as in support of channel program execution. For example, thecontrol unit can include control logic to parse and process messages, inaddition to one or more queues, timers, and registers to facilitatecommunication and status monitoring. The I/O communications adapterparses the response message, extracting the status and extended statusinformation, and performs further calculations using the extractedinformation, such as determining an extended measurement word.

One example of an I/O processing system incorporating and using one ormore aspects of the present invention is described with reference toFIG. 1. I/O processing system 100 includes a host system 101, whichfurther includes for instance, a main memory 102, one or more centralprocessing units (CPUs) 104, a storage control element 106, and achannel subsystem 108. The host system 101 may be a large scalecomputing system, such as a mainframe or server. The I/O processingsystem 100 also includes one or more control units 110 and one or moreI/O devices 112, each of which is described below.

Main memory 102 stores data and programs, which can be input from I/Odevices 112. For example, the main memory 102 may include one or moreoperating systems (OSs) 103 that are executed by one or more of the CPUs104. For example, one CPU 104 can execute a Linux® operating system 103and a z/OS® operating system 103 as different virtual machine instances.The main memory 102 is directly addressable and provides for high-speedprocessing of data by the CPUs 104 and the channel subsystem 108.

CPU 104 is the controlling center of the I/O processing system 100. Itcontains sequencing and processing facilities for instruction execution,interruption action, timing functions, initial program loading, andother machine-related functions. CPU 104 is coupled to the storagecontrol element 106 via a connection 114, such as a bidirectional orunidirectional bus.

Storage control element 106 is coupled to the main memory 102 via aconnection 116, such as a bus; to CPUs 104 via connection 114; and tochannel subsystem 108 via a connection 118. Storage control element 106controls, for example, queuing and execution of requests made by CPU 104and channel subsystem 108.

In an exemplary embodiment, channel subsystem 108 provides acommunication interface between host system 101 and control units 110.Channel subsystem 108 is coupled to storage control element 106, asdescribed above, and to each of the control units 110 via a connection120, such as a serial link. Connection 120 may be implemented as anoptical link, employing single-mode or multi-mode waveguides in a FibreChannel fabric. Channel subsystem 108 directs the flow of informationbetween I/O devices 112 and main memory 102. It relieves the CPUs 104 ofthe task of communicating directly with the I/O devices 112 and permitsdata processing to proceed concurrently with I/O processing. The channelsubsystem 108 uses one or more channel paths 122 as the communicationlinks in managing the flow of information to or from I/O devices 112. Asa part of the I/O processing, channel subsystem 108 also performs thepath-management functions of testing for channel path availability,selecting an available channel path 122 and initiating execution of theoperation with the I/O devices 112.

Each channel path 122 includes a channel 124 (channels 124 are locatedwithin the channel subsystem 108, in one example, as shown in FIG. 1),one or more control units 110 and one or more connections 120. Inanother example, it is also possible to have one or more dynamicswitches (not depicted) as part of the channel path 122. A dynamicswitch is coupled to a channel 124 and a control unit 110 and providesthe capability of physically interconnecting any two links that areattached to the switch. In another example, it is also possible to havemultiple systems, and therefore multiple channel subsystems (notdepicted) attached to control unit 110.

Also located within channel subsystem 108 are subchannels (not shown).One subchannel is provided for and dedicated to each I/O device 112accessible to a program through the channel subsystem 108. A subchannel(e.g., a data structure, such as a table) provides the logicalappearance of a device to the program. Each subchannel providesinformation concerning the associated I/O device 112 and its attachmentto channel subsystem 108. The subchannel also provides informationconcerning I/O operations and other functions involving the associatedI/O device 112. The subchannel is the means by which channel subsystem108 provides information about associated I/O devices 112 to CPUs 104,which obtain this information by executing I/O instructions.

Channel subsystem 108 is coupled to one or more control units 110. Eachcontrol unit 110 provides logic to operate and control one or more I/Odevices 112 and adapts, through the use of common facilities, thecharacteristics of each I/O device 112 to the link interface provided bythe channel 124. The common facilities provide for the execution of I/Ooperations, indications concerning the status of the I/O device 112 andcontrol unit 110, control of the timing of data transfers over thechannel path 122 and certain levels of I/O device 112 control.

Each control unit 110 is attached via a connection 126 (e.g., a bus) toone or more I/O devices 112. I/O devices 112 receive information orstore information in main memory 102 and/or other memory. Examples ofI/O devices 112 include card readers and punches, magnetic tape units,direct access storage devices, displays, keyboards, printers, pointingdevices, teleprocessing devices, communication controllers and sensorbased equipment, to name a few.

One or more of the above components of the I/O processing system 100 arefurther described in “IBM® z/Architecture Principles of Operation,”Publication No. SA22-7832-05, 6th Edition, April 2007; U.S. Pat. No.5,461,721 entitled “System For Transferring Data Between I/O Devices AndMain Or Expanded Storage Under Dynamic Control Of Independent IndirectAddress Words (IDAWS),” Cormier et al., issued Oct. 24, 1995; and U.S.Pat. No. 5,526,484 entitled “Method And System For Pipelining TheProcessing Of Channel Command Words,” Casper et al., issued Jun. 11,1996, each of which is hereby incorporated herein by reference in itsentirety. IBM is a registered trademark of International BusinessMachines Corporation, Armonk, N.Y., USA. Other names used herein may beregistered trademarks, trademarks or product names of InternationalBusiness Machines Corporation or other companies.

In one embodiment, to transfer data between I/O devices 112 and memory102, channel command words (CCWs) are used. A CCW specifies the commandto be executed, and includes other fields to control processing. Oneexample of a CCW is described with reference to FIG. 2 a. A CCW 200includes, for instance, a command code 202 specifying the command to beexecuted (e.g., read, read backward, control, sense and write); aplurality of flags 204 used to control the I/O operation; for commandsthat specify the transfer of data, a count field 206 that specifies thenumber of bytes in the storage area designated by the CCW to betransferred; and a data address 208 that points to a location in mainmemory that includes data, when direct addressing is employed, or to alist (e.g., contiguous list) of modified indirect data address words(MIDAWs) to be processed, when modified indirect data addressing isemployed. Modified indirect addressing is further described in U.S.application Ser. No. 11/464,613, entitled “Flexibly Controlling TheTransfer Of Data Between Input/Output Devices And Memory,” Brice et al.,filed Aug. 15, 2006, which is hereby incorporated herein by reference inits entirety.

One or more CCWs arranged for sequential execution form a channelprogram, also referred to herein as a CCW channel program. The CCWchannel program is set up by, for instance, an operating system, orother software. The software sets up the CCWs and obtains the addressesof memory assigned to the channel program. An example of a CCW channelprogram is described with reference to FIG. 2 b. A CCW channel program210 includes, for instance, a define extent CCW 212 that has a pointer214 to a location in memory of define extent data 216 to be used withthe define extent command. In this example, a transfer in channel (TIC)218 follows the define extent command that refers the channel program toanother area in memory (e.g., an application area) that includes one ormore other CCWs, such as a locate record 217 that has a pointer 219 tolocate record data 220, and one or more read CCWs 221. Each read CCW 220has a pointer 222 to a data area 224. The data area includes an addressto directly access the data or a list of data address words (e.g.,MIDAWs or IDAWs) to indirectly access the data. Further, CCW channelprogram 210 includes a predetermined area in the channel subsystemdefined by the device address called the subchannel for status 226resulting from execution of the CCW channel program.

The processing of a CCW channel program is described with reference toFIG. 3, as well as with reference to FIG. 2 b. In particular, FIG. 3shows an example of the various exchanges and sequences that occurbetween a channel and a control unit when a CCW channel program isexecuting. The link protocol used for the communications is FICON (FibreConnectivity), in this example. Information regarding FICON is describedin “Fibre Channel Single Byte Command Code Sets-3 Mapping Protocol(FC-SB-3), T11/Project 1357-D/Rev. 1.6, INCITS (March 2003), which ishereby incorporated herein by reference in its entirety.

Referring to FIG. 3, a channel 300 opens an exchange with a control unit302 and sends a define extent command and data associated therewith 304to control unit 302. The command is fetched from define extent CCW 212(FIG. 2 b) and the data is obtained from define extent data area 216.The channel 300 uses TIC 218 to locate the locate record CCW and theread CCW. It fetches the locate record command 305 (FIG. 3) from thelocate record CCW 217 (FIG. 2 b) and obtains the data from locate recorddata 220. The read command 306 (FIG. 3) is fetched from read CCW 221(FIG. 2 b). Each is sent to the control unit 302.

The control unit 302 opens an exchange 308 with the channel 300, inresponse to the open exchange of the channel 300. This can occur beforeor after locate command 305 and/or read command 306. Along with the openexchange, a response (CMR) is forwarded to the channel 300. The CMRprovides an indication to the channel 300 that the control unit 302 isactive and operating.

The control unit 302 sends the requested data 310 to the channel 300.Additionally, the control unit 302 provides the status to the channel300 and closes the exchange 312. In response thereto, the channel 300stores the data, examines the status and closes the exchange 314, whichindicates to the control unit 302 that the status has been received.

The processing of the above CCW channel program to read 4 k of datarequires two exchanges to be opened and closed and seven sequences. Thetotal number of exchanges and sequences between the channel and controlunit is reduced through collapsing multiple commands of the channelprogram into a TCCB. The channel, e.g., channel 124 of FIG. 1, uses aTCW to identify the location of the TCCB, as well as locations foraccessing and storing status and data associated with executing thechannel program. The TCW is interpreted by the channel and is not sentor seen by the control unit.

One example of a channel program to read 4 k of data, as in FIG. 2 b,but includes a TCCB, instead of separate individual CCWs, is describedwith reference to FIG. 4. As shown, a channel program 400, referred toherein as a TCW channel program, includes a TCW 402 specifying alocation in memory of a TCCB 404, as well as a location in memory of adata area 406 or a TIDAL 410 (i.e., a list of transfer mode indirectdata address words (TIDAWs), similar to MIDAWs) that points to data area406, and a status area 408. TCWs, TCCBs, and status are described infurther detail below.

The processing of a TCW channel program is described with reference toFIG. 5. The link protocol used for these communications is, forinstance, Fibre Channel Protocol (FCP). In particular, three phases ofthe FCP link protocol are used, allowing host bus adapters to be usedthat support FCP to perform data transfers controlled by CCWs. FCP andits phases are described further in “Information Technology—FibreChannel Protocol for SCSI, Third Version (FCP-3),” T10 Project 1560-D,Revision 4, Sep. 13, 2005, which is hereby incorporated herein byreference in its entirety.

Referring to FIG. 5, a channel 500 opens an exchange with a control unit502 and sends TCCB 504 to the control unit 502. In one example, the TCCB504 and sequence initiative are transferred to the control unit 502 in aFCP command, referred to as FCP_CMND information unit (IU) or atransport command IU. The control unit 502 executes the multiplecommands of the TCCB 504 (e.g., define extent command, locate recordcommand, read command as device control words (DCWs)) and forwards data506 to the channel 500 via, for instance, a FCP_Data IU. It alsoprovides status and closes the exchange 508. As one example, finalstatus is sent in a FCP status frame that has a bit active in, forinstance, byte 10 or 11 of the payload of a FCP_RSP IU, also referred toas a transport response IU. The FCP_RES_IU payload may be used totransport FICON ending status along with additional status information,including parameters that support the calculation of extendedmeasurement words and notify the channel 500 of the maximum number ofopen exchanges supported by the control unit 502.

In a further example, to write 4 k of customer data, the channel 500uses the FCP link protocol phases, as follows:

1. Transfer a TCCB in the FCP_CMND IU.

2. Transfer the IU of data, and sequence initiative to the control unit502.

3. Final status is sent in a FCP status frame that has a bit active in,for instance, byte 10 or 11 of the FCP_RSP IU Payload. The FCP_RES_INFOfield or sense field is used to transport FICON ending status along withadditional status information, including parameters that support thecalculation of extended measurement words and notify the channel 500 ofthe maximum number of open exchanges supported by the control unit 502.

By executing the TCW channel program of FIG. 4, there is only oneexchange opened and closed (see also FIG. 5), instead of two exchangesfor the CCW channel program of FIG. 2 b (see also FIG. 3). Further, forthe TCW channel program, there are three communication sequences (seeFIGS. 4-5), as compared to seven sequences for the CCW channel program(see FIGS. 2 b-3).

The number of exchanges and sequences remain the same for a TCW channelprogram, even if additional commands are added to the program. Compare,for example, the communications of the CCW channel program of FIG. 6with the communications of the TCW channel program of FIG. 7. In the CCWchannel program of FIG. 6, each of the commands (e.g., define extentcommand 600, locate record command 601, read command 602, read command604, read command 606, locate record command 607 and read command 608)are sent in separate sequences from channel 610 to control unit 612.Further, each 4 k block of data (e.g., data 614-620) is sent in separatesequences from the control unit 612 to the channel 610. This CCW channelprogram requires two exchanges to be opened and closed (e.g., openexchanges 622, 624 and close exchanges 626, 628), and fourteencommunications sequences. This is compared to the three sequences andone exchange for the TCW channel program of FIG. 7, which accomplishesthe same task as the CCW channel program of FIG. 6.

As depicted in FIG. 7, a channel 700 opens an exchange with a controlunit 702 and sends a TCCB 704 to the control unit 702. The TCCB 704includes the define extent command, the two locate record commands, andthe four read commands in DCWs, as described above. In response toreceiving the TCCB 704, the control unit 702 executes the commands andsends, in a single sequence, the 16k of data 706 to the channel 700.Additionally, the control unit 702 provides status to the channel 700and closes the exchange 708. Thus, the TCW channel program requires muchless communications to transfer the same amount of data as the CCWchannel program of FIG. 6.

Turning now to FIG. 8, one embodiment of the control unit 110 and thechannel 124 of FIG. 1 that support TCW channel program execution aredepicted in greater detail. The control unit 110 includes CU controllogic 802 to parse and process command messages containing a TCCB, suchas the TCCB 704 of FIG. 7, received from the channel 124 via theconnection 120. The CU control logic 802 can extract DCWs and controldata from the TCCB received at the control unit 110 to control a device,for instance, I/O device 112 via connection 126. The CU control logic802 sends device commands and data to the I/O device 112, as well asreceives status information and other feedback from the I/O device 112.For example, the I/O device 112 may be busy because of a previousreservation request targeting I/O device 112. To manage potential devicereservation contention issues that can arise when the control unit 110receives multiple requests to access the same I/O device 112, the CUcontrol logic 802 keeps track of and stores device busy messages andassociated data in a device busy queue 804. In an exemplary embodiment,an OS 103 of FIG. 1 reserves I/O device 112 to keep other OSs 103 fromaccessing the I/O device 112 while the reservation is active. Althoughdevice reservation is not required for all I/O operations, devicereservation can be used to support operations that necessitate exclusiveaccess for a fixed duration of time, e.g., disk formatting.

The CU control logic 802 can access and control other elements withinthe control unit 110, such as CU timers 806 and CU registers 808. The CUtimers 806 may include multiple timer functions to track how much time asequence of I/O operations takes to complete. The CU timers 806 mayfurther include one or more countdown timers to monitor and abort I/Ooperations and commands that do not complete within a predeterminedperiod. The CU registers 808 can include fixed values that provideconfiguration and status information, as well as dynamic statusinformation that is updated as commands are executed by the CU controllogic 802. The control unit 110 may further include other buffer ormemory elements (not depicted) to store multiple messages or statusinformation associated with communications between the channel 124 andthe I/O device 112. The CU registers 808 may include a maximum controlunit exchange parameter that defines the maximum number of open controlunit exchanges that the control unit 110 supports.

The channel 124 in the channel subsystem 108 includes multiple elementsto support communication with the control unit 110. For example, thechannel 124 may include CHN control logic 810 that interfaces with CHNsubsystem timers 812 and CHN subsystem registers 814. In an exemplaryembodiment, the CHN control logic 810 controls communication between thechannel subsystem 108 and the control unit 110. The CHN control logic810 may directly interface to the CU control logic 802 via theconnection 120 to send commands and receive responses, such as transportcommand and response IUs. Alternatively, messaging interfaces and/orbuffers (not depicted) can be placed between the CHN control logic 810and the CU control logic 802. The CHN subsystem timers 812 may includemultiple timer functions to track how much time a sequence of I/Ooperations takes to complete, in addition to the time tracked by thecontrol unit 110. The CHN subsystem timers 812 may further include oneor more countdown timers to monitor and abort command sequences that donot complete within a predetermined period. The CHN subsystem registers814 can include fixed values that provide configuration and statusinformation, as well as dynamic status information, updated as commandsare transported and responses are received.

One example of a response message 900, e.g., a transport response IU,communicated from the control unit 110 to the channel 124 uponcompletion of a TCW channel program is depicted in FIG. 9. The responsemessage 900 provides status information to the channel 124 and mayindicate that an open exchange between the channel 124 and the controlunit 110 should be closed. The status information provided when a TCWchannel program (e.g., as depicted in FIGS. 5 and 7) is executedincludes additional information beyond the status information sent uponcompletion of a CCW channel program (e.g., as depicted in FIGS. 3 and6). The response message 900 includes a status section 902 and anextended status section 904. When the channel 124 receives the responsemessage 900, it stores parts of status section 902 in the subchannel forthe device the TCW was operating with and the extended status section904 in a memory location defined by the TCW associated with the TCWchannel program that triggered the response message 900. For example, aTCW can designate a section of main memory 102 of FIG. 1 for storage ofthe extended status section 904.

The status section 902 of the response message 900 can include multiplefields, such as an address header 906, status flags one 908, maximumcontrol unit exchange parameter 910, response flags 912, response code914, residual count 916, response length 918, reserved location 920,SPC-4 sense type 922, status flags two 924, status flags three 926,device status 928, and a longitudinal redundancy check (LRC) word 930.Each field in the status section 902 is assigned to a particular byteaddress to support parsing of the response message 900. Although onearrangement of fields within the status section 902 is depicted in FIG.9, it will be understood that the order of fields can be rearranged toalternate ordering within the scope of the disclosure. Moreover, fieldsin the response message 900 can be omitted or combined within the scopeof the invention, e.g., combining status flags two 924 and three 926into a single field. SPC-4 is further described in “SCSI PrimaryCommands-4 (SPC-4)”, Project T10/1731-D, Rev 11, INCITS (May 2007),which is hereby incorporated herein by reference in its entirety.

In an exemplary embodiment, the address header 906 is set to the samevalue as the value received by the control unit 110 in the TCCB thatinitiated the TCW channel program. Although the address header 906 isnot required, including the address header 906 may support testing totrace command and response messages on an I/O device 112 while multipleI/O devices 112 are being accessed.

Status flags one 908 may indicate information such as the success statusof an I/O operation. Multiple bits within the status flags one 908 canprovide additional status information.

The maximum control unit exchange parameter 910 identifies the maximumnumber of exchanges that the control unit 110 allows the channel 124 toopen to it. A value of zero may inform the channel 124 that the controlunit 110 is not altering the current value that the channel 124 isusing. In an exemplary embodiment, the channel 124 establishes a defaultvalue for the maximum number of open exchanges, e.g. 64, which thecontrol unit 110 can modify via the maximum control unit exchangeparameter 910. The value of the maximum control unit exchange parameter910 sent in the response message 900 may be the actual value desired ora seed value for an equation. For example, the value in the maximumcontrol unit exchange parameter 910 can be incremented and/or multipliedby the channel 124 to determine the actual maximum number of openexchanges, e.g. a value of “1” interpreted as “32” by the channel 124.

Using a default value for the maximum number of open exchanges giveseach control unit 110 and channel 124 a common starting point that canbe modified as determined by the control unit 110. In one embodiment,the channel 124 checks the maximum control unit exchange parameter 910received in the response message 900 from the control unit 110 todetermine if the maximum control unit exchange parameter 910 is lowerthan the default value or a previously received value. If the new numberis smaller than the current number of open exchanges, the channel 124does not drive new I/O commands to the control unit 110 until thecurrent number of exchanges used is less than the new limit.

In an exemplary embodiment, the response flags field 912 uses thestandard definition as defined in FCP and can be set to default value,e.g., two. The response code 914 may be equivalent to a Small ComputerSystem Interface (SCSI) status field and can be set to a default value,such as zero. The residual count 916 for read or write commandsindicates the difference between how many bytes were commanded to beread or written versus the number of bytes that actually were read orwritten. The response length 918 is an additional count of bytes ofinformation in the response message 900 after the reserved location 920.The response length 918 supports variable sized response messages 900.The SPC-4 sense type 922 can be assigned to a particular value basedupon message type, e.g., a transport response IU=7F hexadecimal. In oneembodiment, the status flags two 924 is set to a value of 80 hexadecimalto indicate that the I/O operation completed, with a valid value of theresidual count 916. Status flags three 926 is set to a value of one whenthe I/O operation completed, indicating that extended status 904 isincluded as part of the response message 900. The device status 928relays status information generated by the I/O device 112. The LRC word930 is a check word that covers the other fields in the status section902 of the response message 900 to verify the integrity of the statussection 902. The LRC word 930 can be generated through applying anexclusive-or operation to an initial seed value with each field includedin the LRC calculation in succession.

The extended status section 904 provides information to the channelsubsystem 108 and the OS 103 associated with operating the control unit110 in a transport mode capable of running a TCW channel program. Theextended status section 904 may support configurable definitions withdifferent type status definitions for each type. In an exemplaryembodiment, the extended status section 904 includes a transport statusheader (TSH) 932, a transport status area (TSA) 934, and an LRC word 936of the TSH 932 and the TSA 934. The TSH 932 may include extended statuslength 940, extended status flags 942, a DCW offset 944, a DCW residualcount 946, and a reserved location 948. The TSH 932 is common for thedifferent formats, with the each format defined by a type code in theextended status flags 942. The TSA 934 may include a total device timeparameter 950, defer time parameter 952, queue time parameter 954,device busy time parameter 956, device active only time parameter 958,and appended device sense data 960. Each of these fields is described ingreater detail in turn.

The extended status length 940 is the size of the extended statussection 904. In an exemplary embodiment, the extended status flags 942has the following definition:

Bit 0—The DCW offset 944 is valid.

Bit 1—The DCW residual count 946 is valid.

Bit 2—This bit set to a one informs the OS 103 of FIG. 1 in a definitivemanner when the control unit 110 had to access slow media for data,e.g., a cache miss.

Bit 3—Time parameters 950-958 are valid. The type code set to a one andthis bit set to a one indicates that all or the time parameters 950-958are valid.

Bit 4—Reserved.

Bits 5 to 7—These three bits are the type code that defines the formatof the TSA 934 of the extended status section 904. The names of theencodes are:

-   -   0. Reserved.    -   1. I/O Status. The extended status section 904 contains valid        ending status for the transport-mode I/O operation.    -   2. I/O Exception. The extended status section 904 contains        information regarding termination of the transport-mode I/O        operation due to an exception condition.    -   3. Interrogate Status. The extended status section 904 contains        status for an interrogate operation.    -   4. to 7. Reserved.

The DCW offset 944 indicates an offset in the TCCB of a failed DCW.Similarly, the DCW residual count 946 indicates the residual byte countof a failed DCW (i.e., where execution of the DCWs was interrupted).

In an exemplary embodiment, the TSA 934 definition when the type code ofES flags 942 indicates a type of I/O Status includes time parameters950-958, as well as optionally appended device sense data 960. The timeparameters 950-958 represent time values and can be scaled to any timeunits, such as microseconds. The CU timers 806 of FIG. 8 are used tocalculate the time parameters 950-958, and the CU registers 808 can alsobe employed to capture values of the CU timers 806 on a triggeringevent.

The total device time parameter 950 is the elapsed time from when thecontrol unit 110 received the transport command IU until it sent thetransport response IU (i.e., response message 900) for the I/Ooperation. The defer time parameter 952 indicates control unit defertime. This is the time accumulated by the control unit 110 working withthe I/O device 112 when no communication with the channel 124 isperformed. On CCW channel programs, such as that depicted in FIG. 3, thecontrol unit 302 disconnects from the channel 300 during this time.

The queue time parameter 954 is the time that an I/O operation is queuedat the control unit 110, but does not include queue time for device busytime where the I/O device 112 is reserved by another channel 124 undercontrol of a different OS 103 on the same system or on another system.The device busy time parameter 956 is the time that a transport commandIU is queued at the control unit 110 waiting on a device busy caused bythe I/O device 112 being reserved by another channel 124 under controlof a different OS 103 on the same system or on another system.

The device active only time parameter 958 is the elapsed time between achannel end (CE) and a device end (DE) at the control unit 110, when thecontrol unit 110 holds the CE until DE is available. The CE may indicatethat the portion of an I/O operation involving a transfer of data orcontrol information between the channel 124 and the control unit 110 hasbeen completed. The DE may indicate that the device portion of an I/Ooperation is completed. The appended device sense data 960 issupplemental status that the control unit 110 provides conditionally inresponse to an active unit check (UC) bit in the device status 928.

The LRC word 936 is a longitudinal redundancy check word of the TSH 932and the TSA 934, calculated in a similar fashion as the LRC word 930 inthe status 902 section of the response message 900. The LRC word 936 canbe calculated on a variable number of words, depending upon the numberof words included in the appended device sense data 960.

FIG. 10 depicts an exemplary timing diagram 1000 illustrating how thetime parameters 950-958 are calculated in relation to each other, aswell as other time values calculated by the channel subsystem 108 ofFIG. 8. It will be understood that the timing diagram 1000 depicts oneexample of a timing sequence, and as such, may vary depending uponresponse times of various I/O processing system elements. At startsubchannel A 1002, the channel subsystem 108 captures a starting timevalue using the CHN subsystem timers 812 and the CHN subsystem registers814 of FIG. 8. After an initial processing and communication propagationdelay, the channel 124 sends a transport command IU to the control unit110. The control unit 110 receives the transport command IU and createsa time stamp of transport command IU C 1004 using the CU timers 806 andthe CU registers 808. The control unit 110 parses the transport commandIU to extract DCWs and send commands to a targeted I/O device, such asthe I/O device 112. The I/O device 112 may be busy completing a commandfrom another channel 124 under control of a different OS 103 on the samesystem or on another system. The control unit 110 uses the CU timers 806to track device busy time 1006 and writes the value to the device busytime parameter 956 of the response message 900 of FIG. 9. If anotherchannel 124 under control of a different OS 103 on the same system or onanother system attempts to reserve or use the same I/O device 112,multiple requests are queued on the device busy queue 804. The waitingtime associated with the device busy queue 804 is included in the devicebusy time 1006.

In I/O processing systems that run CCW channel programs, the controlunit 110 provides a command response at time CMR B 1008 to acknowledgethat an initial command has been received, and the control unit 110 isready for additional commands. However, when a TCW channel program isrun, the control unit 110 does not respond at time CMR B 1008; rather,the control unit 110 waits until the TCW channel program terminates toprovide a response message to the channel 124, such as the responsemessage 900 of FIG. 9. Thus, to perform extended measurementcalculations that utilize time CMR B 1008, I/O processing systems thatrun TCW channel programs must employ an alternate approach to derivetiming information.

Queue time 1010 indicates time that an I/O operation is queued at thecontrol unit 110, but does not include the queue time for the devicebusy time 1006, where the I/O device 112 is reserved by another channel124 under control of a different OS 103 on the same system or on anothersystem. The queue time 1010 is written to the queue time parameter 954in the response message 900 of FIG. 9.

The time accumulated by the control unit 110 working with the I/O device112 is illustrated as CU defer time 1012 in FIG. 10. The CU defer time1012 is written to the defer time parameter 952 in the response message900 of FIG. 9.

Device active only time 1014 represents time between CE and DE at thecontrol unit 110, if the control unit 110 does not present CE statusuntil the DE status is available. The device active only time 1014 iswritten to the device active only time parameter 958 in the responsemessage 900 of FIG. 9.

Once the control unit 110 completes the I/O operation requested in thetransport command IU, the control unit 110 sends a transport responseIU, e.g., the response message 900 of FIG. 9, to the channel 124 atcontrol unit response IU D 1016 time stamp. Total device time 1018 canbe calculated as the difference between the time stamps of control unitresponse IU D 1016 and transport command IU C 1004. The total devicetime 1018 is written to the total device time parameter 950 in theresponse message 900 of FIG. 9. In response to the channel 124 receivingthe transport response IU, total channel time 1020 can be calculated asthe time from when the channel 124 sent the transport command IU to thecontrol unit 110, until when the channel 124 received the transportresponse IU. At time stamp ending status E 1022, the channel 124identifies that an ending status was received in the transport responseIU from the control unit 110. The channel subsystem 108 calculates totalsystem I/O operation time 1024 as the time difference between time stampending status E 1022 and start subchannel A 1002.

In an exemplary embodiment, an extended measurement word (EMW) includingmultiple time values provides I/O measurement information for I/Ooperations performed at the channel 124 or a subchannel. The channelsubsystem 108 can use the time parameters 950-958 received in theresponse message 900 along with time values derived from the CHNsubsystem timers 812 to calculate the EMW. The EMW may be stored in theCHN subsystem registers 814 or written to the main memory 102 of FIG. 1.The EMW includes a device connect time, a function pending time, adevice disconnect time, a control unit queuing time, a device activeonly time, a device busy time, and an initial command response time. Thedevice connect time is calculated as total device time parameter950−defer time parameter 952−device busy time parameter 956−deviceactive only time parameter 958. While the function pending time iscalculated in an I/O processing system supporting CCW channel programsas CMR B 1008−start subchannel A 1002, an I/O processing systemsupporting TCW channel programs can calculate the function pending timeas the total system I/O operation time 1024−the total device timeparameter 950. The device disconnect time is set equal to the defer timeparameter 952. The control unit queuing time is set equal to the queuetime parameter 954. The device active only time is calculated as thetime between CE and DE at the channel 124+the device active only timeparameter 958. The device busy time is calculated as the device busytime parameter 956+any other device busy time information available tothe channel subsystem 108. The initial command response time iscalculated as total channel time 1020−the total device time parameter950. The EMW time values can provide the OS 103 of FIG. 1 with insightas to the performance, congestion, and efficiency of I/O operationsoccurring at the I/O devices 112. The OS 103 or a higher-levelapplication program may respond in turn by altering I/O operationrequests to better balance elements of the I/O processing system 100 andreduce delays.

Turning now to FIG. 11, a process 1100 for determining an extendedmeasurement word at a channel subsystem of an I/O processing systemusing data from a control unit will now be described in accordance withexemplary embodiments, and in reference to the I/O processing system 100of FIG. 1. At block 1102, the channel 124 in the channel subsystem 108sends a command message to the control unit 110. The command message maybe a transport command IU, including a TCCB with multiple DCWs as partof a TCW channel program. The control unit 110 receives the commandmessage, parses it, and initiates I/O operations as commanded in theDCWs to the I/O device 112. Upon termination of the TCW channel programon the control unit 110, the control unit 110 reports status informationto the channel 124 in a transport response IU message (e.g., responsemessage 900 of FIG. 9, including a status section 902 and an extendedstatus section 904). The transport response IU message includes aplurality of time values as determined by the control unit 110, such asthe time parameters 950-958 of FIG. 9 as determined using the CU timers806 of FIG. 8.

At block 1104, the channel subsystem 108 receives the transport responseIU message in response to sending the command message to the controlunit 110. Communication between the channel subsystem 108 and thecontrol unit 110 may be managed by the CU control logic 802 and the CHNcontrol logic 810 of FIG. 8 for a specific channel 124 of the channelsubsystem 108.

At block 1106, the channel subsystem 108 extracts a plurality of timevalues from the transport response IU message as calculated by thecontrol unit 110. For example, the time values may be extracted from theextended status section 904 of the response message 900 of FIG. 9, wherethe response message 900 depicts one embodiment of the transportresponse IU message.

At block 1108, the channel subsystem 108 calculates an extendedmeasurement word as a function of the time values. The extendedmeasurement word can include a number of time values, such as a deviceconnect time, a function pending time, a device disconnect time, acontrol unit queuing time, a device active only time, a device busytime, and an initial command response time. Some of the time values inthe extended measurement word may also incorporate values calculated atthe channel subsystem 108, such as total channel time and total systemI/O operation time. Time values calculated at the channel subsystem 108can utilize one or more CHN subsystem timers 812 of FIG. 8 to provide atime base.

At block 1110, the channel subsystem 108 writes the extended measurementword to computer readable memory in the I/O processing system 100, suchas the main memory 102. The channel subsystem 108 may also write thecontents of the extended status section 904 of the response message 900to the main memory 102 for the OS 103 or other programs to access. In anexemplary embodiment, the specific location to write the extended statussection 904 in the I/O processing system 100 is established by a TCWthat includes an address pointer to a desired write location.

Technical effects of exemplary embodiments include determining anenhanced measurement word using time data provided by a control unit inan I/O processing system. The channel receiving the time data can gaininsight into the performance of the control unit and an I/O devicecontrolled by the control unit over a period of time encompassingmultiple I/O operations. Advantages include acquiring timing performancedata without interrupting the execution of a TCW channel program on acontrol unit. Thus, programs designed to gauge performance of CCWchannel programs can gauge the performance of TCW channel programs in aseamless or near seamless fashion, while gaining advantages of highercommunication throughput due in part to exchanging fewer messages perchannel program.

As described above, embodiments can be embodied in the form ofcomputer-implemented processes and apparatuses for practicing thoseprocesses. In exemplary embodiments, the invention is embodied incomputer program code executed by one or more network elements.Embodiments include a computer program product 1200 as depicted in FIG.12 on a computer usable medium 1202 with computer program code logic1204 containing instructions embodied in tangible media as an article ofmanufacture. Exemplary articles of manufacture for computer usablemedium 1202 may include floppy diskettes, CD-ROMs, hard drives,universal serial bus (USB) flash drives, or any other computer-readablestorage medium, wherein, when the computer program code logic 1204 isloaded into and executed by a computer, the computer becomes anapparatus for practicing the invention. Embodiments include computerprogram code logic 1204, for example, whether stored in a storagemedium, loaded into and/or executed by a computer, or transmitted oversome transmission medium, such as over electrical wiring or cabling,through fiber optics, or via electromagnetic radiation, wherein, whenthe computer program code logic 1204 is loaded into and executed by acomputer, the computer becomes an apparatus for practicing theinvention. When implemented on a general-purpose microprocessor, thecomputer program code logic 1204 segments configure the microprocessorto create specific logic circuits.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims. Moreover, the use of the terms first, second, etc. do not denoteany order or importance, but rather the terms first, second, etc. areused to distinguish one element from another. Furthermore, the use ofthe terms a, an, etc. do not denote a limitation of quantity, but ratherdenote the presence of at least one of the referenced item.

1. An article of manufacture comprising at least one computer usable medium having computer readable program code logic to determine an extended measurement word at a channel subsystem of an input/output (I/O) processing system using data from a control unit, the computer readable program code logic for performing a method comprising: sending a command message to the control unit; receiving a transport response information unit message at the channel subsystem in response to sending the command message to the control unit; extracting a plurality of time values from the transport response information unit message as calculated by the control unit; calculating an extended measurement word as a function of the extracted time values; and writing the calculated extended measurement word to computer readable memory in the I/O processing system.
 2. The article of manufacture of claim 1 wherein the computer readable program code logic performing the method further comprises: storing a start subchannel time prior to sending the command message to the control unit; storing an ending status time upon identifying an ending status in the transport response information unit message; and determining a total system I/O operation time at the channel subsystem as a time difference value between the ending status time and the start subchannel time.
 3. The article of manufacture of claim 2 wherein the extracted time values include a total device time parameter indicating elapsed time from when the control unit received the command message until the control unit transmitted the transport response information unit message for a device I/O operation; and the calculated extended measurement word includes a function pending time calculated as a time difference value between the total system I/O operation time and the total device time parameter.
 4. The article of manufacture of claim 1 wherein the computer readable program code logic performing the method further comprises: storing a sending time at the channel subsystem upon sending the command message to the control unit; storing a receiving time upon receiving the transport response information unit message at the channel subsystem; and determining a total channel time at the channel subsystem as a time difference value between the receiving time and the sending time.
 5. The article of manufacture of claim 4 wherein the extracted time values include a total device time parameter indicating elapsed time from when the control unit received the command message until the control unit transmitted the transport response information unit message for a device I/O operation; and the calculated extended measurement word includes an initial command response time calculated as a time difference value between the total channel time and the total device time parameter.
 6. The article of manufacture of claim 1 wherein the extracted time values include: a total device time parameter indicating elapsed time from when the control unit received the command message until the control unit transmitted the transport response information unit message for a device I/O operation; a defer time parameter indicating control unit defer time; a device busy time parameter indicating elapsed time that the command message was queued at the control unit waiting on a reserved device; and a device active only time parameter indicating elapsed time between a channel end (CE) and a device end (DE) at the control unit in response to the control unit holding the CE until the DE is available, and further wherein the calculated extended measurement word includes a device connect time calculated as a time difference value between the total device time parameter, the defer time parameter, the device busy time parameter and the device active only time parameter.
 7. The article of manufacture of claim 1 wherein the extracted time values include a defer time parameter indicating control unit defer time and a queue time parameter indicating elapsed time that an I/O operation was queued at the control unit excluding queue time for a reserved device, and further wherein the calculated extended measurement word includes a device disconnect time set equal to the defer time parameter and a control unit queuing time set equal to the queue time parameter.
 8. The article of manufacture of claim 1 wherein the computer readable program code logic performing the method further comprises: determining an elapsed time between a channel end (CE) and a device end (DE) at the channel subsystem, wherein the extracted time values include a device active only time parameter, and the calculated extended measurement word includes a device active only time calculated as a time summation value of the elapsed time and the device active only time parameter.
 9. The article of manufacture of claim 1 wherein the extracted time values include a device busy time parameter indicating elapsed time that the command message was queued at the control unit waiting on a reserved device; and the calculated extended measurement word includes a device busy time calculated as a time summation value of the device busy time parameter and additional device busy time as determined by the channel subsystem.
 10. The article of manufacture of claim 1 wherein the extracted time values are extracted from an extended status section of the transport response information unit message.
 11. An apparatus for determining an extended measurement word in an input/output (I/O) processing system, the apparatus comprising: a channel subsystem in communication with a control unit, the channel subsystem configured to perform a method comprising: sending a command message to the control unit; receiving a transport response information unit message at the channel subsystem in response to sending the command message to the control unit; extracting a plurality of time values from the transport response information unit message as calculated by the control unit; calculating an extended measurement word as a function of the extracted time values; and writing the calculated extended measurement word to computer readable memory in the I/O processing system.
 12. The apparatus of claim 11 wherein the method further comprises: storing a start subchannel time prior to sending the command message to the control unit; storing an ending status time upon identifying an ending status in the transport response information unit message; and determining a total system I/O operation time at the channel subsystem as a time difference value between the ending status time and the start subchannel time.
 13. The apparatus of claim 12 wherein the extracted time values include a total device time parameter indicating elapsed time from when the control unit received the command message until the control unit transmitted the transport response information unit message for a device I/O operation; and the calculated extended measurement word includes a function pending time calculated as a time difference value between the total system I/O operation time and the total device time parameter.
 14. The apparatus of claim 11 wherein the channel subsystem further performs: storing a sending time at the channel subsystem upon sending the command message to the control unit; storing a receiving time upon receiving the transport response information unit message at the channel subsystem; and determining a total channel time at the channel subsystem as a time difference value between the receiving time and the sending time.
 15. The apparatus of claim 14 wherein the extracted time values include a total device time parameter indicating elapsed time from when the control unit received the command message until the control unit transmitted the transport response information unit message for a device I/O operation; and the calculated extended measurement word includes an initial command response time calculated as a time difference value between the total channel time and the total device time parameter.
 16. The apparatus of claim 11 wherein the extracted time values include: a total device time parameter indicating elapsed time from when the control unit received the command message until the control unit transmitted the transport response information unit message for a device I/O operation; a defer time parameter indicating control unit defer time; a device busy time parameter indicating elapsed time that the command message was queued at the control unit waiting on a reserved device; and a device active only time parameter indicating elapsed time between a channel end (CE) and a device end (DE) at the control unit in response to the control unit holding the CE until the DE is available, and further wherein the calculated extended measurement word includes a device connect time calculated as a time difference value between the total device time parameter, the defer time parameter, the device busy time parameter and the device active only time parameter.
 17. The apparatus of claim 11 wherein the extracted time values include a defer time parameter indicating control unit defer time and a queue time parameter indicating elapsed time that an I/O operation was queued at the control unit excluding queue time for a reserved device, and further wherein the calculated extended measurement word includes a device disconnect time set equal to the defer time parameter and a control unit queuing time set equal to the queue time parameter.
 18. The apparatus of claim 11 wherein the channel subsystem includes a channel subsystem timer, and the channel subsystem further performs: determining an elapsed time between a channel end (CE) and a device end (DE) at the channel subsystem using the channel subsystem timer, wherein the extracted time values include a device active only time parameter, and the calculated extended measurement word includes a device active only time calculated as a time summation value of the elapsed time and the device active only time parameter.
 19. The apparatus of claim 11 wherein the extracted time values include a device busy time parameter indicating elapsed time that the command message was queued at the control unit waiting on a reserved device; and the calculated extended measurement word includes a device busy time calculated as a time summation value of the device busy time parameter and additional device busy time as determined by the channel subsystem.
 20. The apparatus of claim 11 wherein the extracted time values are extracted from an extended status section of the transport response information unit message.
 21. A method for determining an extended measurement word at a channel subsystem of an input/output (I/O) processing system using data from a control unit, the method comprising: sending a command message to the control unit; receiving a transport response information unit message at the channel subsystem in response to sending the command message to the control unit; extracting a plurality of time values from the transport response information unit message as calculated by the control unit; calculating an extended measurement word as a function of the extracted time values; and writing the calculated extended measurement word to computer readable memory in the I/O processing system.
 22. The method of claim 21 further comprising: storing a start subchannel time prior to sending the command message to the control unit; storing an ending status time upon identifying an ending status in the transport response information unit message; and determining a total system I/O operation time at the channel subsystem as a time difference value between the ending status time and the start subchannel time, wherein the extracted time values include a total device time parameter and the calculated extended measurement word includes a function pending time calculated as a time difference value between the total system I/O operation time and the total device time parameter.
 23. The method of claim 21 further comprising: storing a sending time at the channel subsystem upon sending the command message to the control unit; storing a receiving time upon receiving the transport response information unit message at the channel subsystem; and determining a total channel time at the channel subsystem as a time difference value between the receiving time and the sending time, wherein the extracted time values include a total device time parameter, a defer time parameter, a device busy time parameter and a device active only time parameter, and the calculated extended measurement word includes a device connect time calculated as a time difference value between the total device time parameter, the defer time parameter, the device busy time parameter and the device active only time parameter.
 24. An article of manufacture comprising at least one computer usable medium having computer readable program code logic to determine an extended measurement word at a channel subsystem of an input/output (I/O) processing system using data from a control unit, the computer readable program code logic for performing a method comprising: sending a transport command information unit message including a transport command control block (TCCB) as part of a transport control word (TCW) channel program to the control unit for execution; receiving a transport response information unit message at the channel subsystem in response to sending the transport command information unit message to the control unit, wherein the transport response information unit message includes a status section and an extended status section, the extended status section further including a transport status header (TSH) defining characteristics of a transport status area (TSA) of the extended status section; extracting a plurality of time values from the extended status section of the transport response information unit message as calculated by the control unit using one or more control unit timers, wherein the extracted time values include at least one of a total device time parameter, a defer time parameter, a queue time parameter, a device busy time parameter, a device active only time parameter, and appended device sense data; calculating an extended measurement word as a function of the extracted time values, wherein the calculated extended measurement word includes at least one of a device connect time, a function pending time, a device disconnect time, a control unit queuing time, a device active only time, a device busy time, and an initial command response time; and writing the calculated extended measurement word to computer readable memory in the I/O processing system.
 25. An apparatus for determining an extended measurement word in an input/output (I/O) processing system, the apparatus comprising: a channel subsystem in communication with a control unit, the control unit capable of controlling a device, the channel subsystem configured to perform a method comprising: sending a transport command information unit message including a transport command control block (TCCB) as part of a transport control word (TCW) channel program to the control unit for execution; receiving a transport response information unit message at the channel subsystem in response to sending the transport command information unit message to the control unit, wherein the transport response information unit message includes a status section and an extended status section, the extended status section further including a transport status header (TSH) defining characteristics of a transport status area (TSA) of the extended status section; extracting a plurality of time values from the extended status section of the transport response information unit message as calculated by the control unit using one or more control unit timers, wherein the extracted time values include at least one of a total device time parameter, a defer time parameter, a queue time parameter, a device busy time parameter, a device active only time parameter, and appended device sense data; calculating an extended measurement word as a function of the extracted time values, wherein the calculated extended measurement word includes at least one of a device connect time, a function pending time, a device disconnect time, a control unit queuing time, a device active only time, a device busy time, and an initial command response time; and writing the calculated extended measurement word to computer readable memory in the I/O processing system. 